Parameters selection criteria of proportional-integral controller for a quadratic buck converter

A criteria for selection of parameters of proportional and integral (PI) controller for a DC-DC quadratic buck converter is proposed here. This procedure was developed from a large-signal model of converter in which a multiloop control scheme is added. This scheme has two control loops: an inner current loop, which improves the dynamic behaviour using a single gain, and a conventional PI controller as outer loop, which provides regulation. For the resulting system, the necessary conditions are derived for the existence of equilibrium point and stability in closed-loop. In comparison with the traditional method of loopshaping, which uses small-signal model, analytic expressions are found that simplifies the selection of controller parameters. At the end, the procedure is applied to 28 W quadratic buck regulator prototype and experimental results are given to verify the effectiveness.